@xster please take a look

CC @dnfield

@gaaclarke can you take a look?

Does this bug still exist on master?

I am afraid it still exist

Hm. Both the Android and the iOS embedding believe they can return nullptr in CreateRenderingSurface if they have no surface to work with, which can happen if they get that call without having a view to work with (or, before having a view to work with).

That should only be valid if there really is no View to work with. But in this case, there should be.

I haven't traced this all the way through, but it seems like we might not be calling NotifyCreated properly in this case - it also seems like we should not try to setup the rasterizer if there is in fact no surface to work with.

/cc @chinmaygarde @amirh @cyanglaz

@gaaclarke probably has more recent context on this than I do as well but those people might be interested in the platform view/rasterizer aspects.

@xujim what you're describing sounds reasonable to me. Does it work if you manually set the engine.viewController to nil or to the top vc before the bottom vc gets covered? Seems like that's what https://github.com/xujim/testaccessibility/compare/master...foxsofter:fix_crash?expand=1#diff-a6425004106bb459a3f91283fe144fd2 is doing right?

This bug is essentially asking us to make initWithEngine more ergonomic by having the FlutterViewController remove the previous FlutterViewController from the engine automatically?

Posterity: from chatting with @gaaclarke documentation and ergonomics around this may all end up bundled in the #37644 work as well.

@xster , thanks, fix_crash works for my example, but it needs to hook the UINavigationController, which is not so nice. I finally figured out a workaround, which is better for me——try not call surfaceUpdated:NO for my FlutterViewController. This way, we can make sure the flutter engine holding an ios_surface_ until it is reset by SetOwnerViewController as soon as another FlutterVC is attached to FlutterEngine.

The cons of my solution is that need to override the viewDidDisappear of FlutterViewController, which will lose the TRACE_EVENT0. So, I do believe @gaaclarke 's words that it is not supported flow by flutter:(
Hopefully, you guys can support this flow, I think it is reasonable.
My code as following:

//in this way, we can call FlutterViewController's parent in FLBFlutterViewContainer
@interface FlutterViewController (bridgeToviewDidDisappear)
- (void)flushOngoingTouches;
- (void)override_viewDidDisappear:(BOOL)animated;
@end

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wincomplete-implementation"
@implementation FlutterViewController (bridgeToviewDidDisappear)
- (void)bridge_viewDidDisappear:(BOOL)animated{
//    TRACE_EVENT0("flutter", "viewDidDisappear");
    [self flushOngoingTouches];
    [super viewDidDisappear:animated];
}
@end

//my VC inherited from FlutterViewController
@implementation FLBFlutterViewContainer 
- (void)viewDidDisappear:(BOOL)animated
{
    [BoostMessageChannel didDisappearPageContainer:^(NSNumber *result) {}
                                                pageName:_name
                                                  params:_params
                                                uniqueId:self.uniqueIDString];

    if (FLUTTER_VC.beingPresented || self.beingDismissed /*|| ![self.uniqueIDString isEqualToString:[(FLBFlutterViewContainer*)FLUTTER_VC uniqueIDString]]*/)
    {
        [FLUTTER_APP resume];
        [(FLBFlutterViewContainer*)FLUTTER_VC surfaceUpdated:YES];
    }

    //call super's super implementation
    [self bridge_viewDidDisappear:animated];
}
@end 

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.